Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications.
In lighting systems, such as those that include LED-based light sources, it is desirable to have control over one or more light sources of the lighting system. For example, it may be desirable to have control of which of a plurality of light sources are illuminated and/or to have control of one or more lighting parameters of one or more of the light sources. For example, it may be desirable to control the dimming state of light output provided by one or more LED-based lighting fixtures. Control of the dimming state of a lighting fixture may enable energy savings by preventing over-lighting of an area illuminated by the lighting fixture during certain time periods. For example, control of the dimming state of a lighting fixture may enable dimming of the lighting fixture to a low light output level or a no light output level during time periods when users are not present near the lighting fixture. Also, for example, control of the dimming state of a lighting fixture may additionally and/or alternatively enable dimming of the lighting fixture to a lower light output level when natural daylight (alone or in combination with the light output provided by the lighting fixture) is sufficient to illuminate the area illuminated by the lighting fixture to a desired level. Control of the dimming state of a lighting fixture may additionally and/or alternatively enable a high level of light output to be provided by the lighting fixture during certain time periods, such as during emergencies and/or during cleaning.
Some lighting systems utilize a group lighting controller to control the dimming state of a plurality of lighting fixtures controlled by the group lighting controller. For example, the group lighting controller may receive input from a group daylight sensor and control the dimming state of all lighting fixtures controlled by the group lighting controller based on the received input. For example, in response to input from the group daylight sensor indicating an over-lighting condition, the group lighting controller may provide a control command to all controlled lighting fixtures to cause the light output level of all controlled lighting fixtures to be decreased based on the control command. Also, for example, in response to input from the group daylight sensor indicating an under-lighting condition, the group lighting controller may provide a control command to all controlled lighting fixtures to cause the light output level of all controlled lighting fixtures to be increased based on the control command.
However, such group control of a group of lighting fixtures provides the same control signals to all controlled lighting fixtures, thereby resulting in increases and/or decreases of the light output level of all controlled lighting fixtures in accordance with the control signals. Controls utilizing the mains wiring are popular for office renovation. However, the grouping of the lighting fixtures is inherently pre-determined by the already existing mains wiring of the lighting fixtures in the ceiling. Accordingly, in response to an under-lighting condition indicated by a group daylight sensor, a first lighting fixture located immediately adjacent a window and a second lighting fixture in a window-less corner of the room may both receive the same control command that dictates an increase in light output levels. However, it may be the case that an increase in a light output level at the first lighting fixture in accordance with the group control signals would result in an over-lighting condition at an area illuminated by the first lighting fixture. For example, the daylight contribution via the window immediately adjacent the first lighting fixture may be sufficient to achieve a desired lighting level at the area illuminated by the first lighting fixture, and increasing the light output level of the lighting fixture would actually create an over-lighting condition. It is known that over-lighting is undesirable, as the lux level of the lighting deviates from the optimal level required for specific tasks by the end-user. For instance, it is known that an optimal level for computer aided drafting work may require a lower light level than an optimal level for work that mainly involves reading paper (not on a computer). In addition, over-lighting may result in undesired energy waste. Likewise, it may be the case that an increase in a light output level at the second lighting fixture in accordance with the group control signals would result in an under-lighting condition at an area illuminated by the second lighting fixture. For example, the group daylight sensor may be located in an area that receives more daylight than the second lighting fixture and the increase in light output level at the second lighting fixture based on the control commands may be insufficient to remedy the under-lighting condition at the area illuminated by the second lighting fixture. Individual calibration of lighting fixtures to fine-tune response to received control commands may assist in minimizing such issues. However, individual calibration is cumbersome and prone to user error. Moreover, such lighting systems lack the ability to enable a lighting controller of an individual lighting fixture to receive both individual sensor input and group control input and autonomously determine an appropriate dimming state based on such multiple inputs. Additional and/or alternative drawbacks of such lighting systems may be presented.
Thus, there is a need in the art to provide methods and apparatus that enable control of one or more properties of light output of a lighting fixture based on local input (based on local sensor readings) and group input (provided to the lighting fixture and additional lighting fixtures).